Telechronometer



G. BABCOCK TELECHRONOMETER Sept. l, 1931.

Original Filed Oct. 15, 1921 Patented Sept. 1, 1931 UNITED STATES PATENTOFFICE i, e

GARRISON BABCOCK, OF SEATTLE, WASHINGTON, ASSIGNOR TO AMERICAN TELECHRO-NOMETER COMPANY, OF SEATTLE, IVASHINGTON, A CORPORATION 0F WASHINGTONTELECHRONOMETER Original application filed 0ctober15, 1921, Serial No.508,037. Patent No. 1,747,210, dated February 18, 1930. Divided and thisapplication led April 6, 1929. Serial No. 352,983.

This invention relates to telechronometers, more particularly to a newand improved telechronometer for use on a telephone line.

In my copending application, vSerial No. 508,037, filed October 15,1921, Patent No. 1,747,210, Feb. 18, 1930, of which application thiscase is a division, I disclose a telechronometer and a telephone systememploying that telechronometer. For the full operating details of such asystem, reference is here made to the above copending application.

Briefly, however, the telechronometer comprises an electromagnetic meterlocated at the subscribers premises and operated by reversals of current`over the subscribers line to the telephone office at periodic intervalsduring the conversations over the telephone.

The telephone comprises the usual talking instrumentalities and may beeither a manual telephone or an automatic telephone depending upon thesystem with which it is used.

The telechronometer itself, which is disclosed in detail in the abovementioned copending application, comprises a plurality of dials overwhich creep register indicators which are driven by a ratchet and geararrangement actuated electro-magnetically by the reversal of thepolarity of current flowing over the telephone line.

To bring about this reversal of current, a reversing switch or polechanger is located in the central office and associated with the batteryfeed leads of the cord circuit, in a manual exchange or of the linerelay of the connector or final selector switch of an automatictelephone exchange. Briefly,` this pole changer comprises a plurality ofresistance units, preferably four in number, which are operated in pairsto periodically reverse the polarity of the battery connection to theanswering supervisory relay of the cord circuit. The battery feed forthe transmitter of the calling station is drawn through this relay aswill be well understood by those skilled in the art. The resistanceunits are of the type which vary responsive to the change of pressureupon them and might conveniently be carbon pile resistors. When thepressure on the pile is increased the resistance decreases and thecurrent How correspondingly increases. The driving arrangement for theplungers which alternately compress and decompress theY resistance pilesis arranged so that while one of the pairs of resistances is beingcompressed the other one is being decompressed in the same ratio. .Thebattery supply leads ofthe line relays are connected to bot-h of ancevalues of the two pairs of resistances effects a change in polarity ofthe connection in the manner explained in detail in my above mentionedcopending application.

Inasmuch as the registering mechanism is located at the subscriherspremises, it is desirable that the meter be sealed and protected toprevent unscrupulous subscribers from disabling it Vto thereby reducetheir telephone bills. K

The sealing of the meter-hasbeen `ern- Y ployed heretofore to preventtampering with this mechanism, and while that seal is eective for thatpurpose, it does not guard against the contingency of the subscribershouf-circuiting or grounding the electromagnets of the meter to therebyprevent its operation. v y

In telechronometers devised heretofore the electro-magnets of the meterwere in the line circuit only during conversation and then in such amanner that the detection of a short circuit or a ground connection bytests supplied at the central office was very difhcult. f

Inmy present invention which is based upon the disclosure of the abovecopending application, I have provided a new and improvedelectro-magnetic circuit for the telefA chronometer, which circuit lendsitself to the ready detection of circuit tampering by the subscriber toprevent the operation of the telechronometer.

The electro-magnet of the telechronometer comprises two windings whichare serially connected in the line circuit. The windings are so designedthat when the normal line circuit current is flowing through either oneof them, the meter will be operated. That" QG() these rhecstats so thatthe change in resistcuit to the telephone office is balanced-elec-ytrically.`

Iiftlie subscriber short circuits one `ofthe windings of the meter, theelectrical circuit 1s unbalanced, and the detection of that;

short circuit is made readily possible by the reduced resistance andinductance of the,

line circuit.. The short circuiting of the one winding will not preventthe operation of the metery since the remaining winding is ofsufficient' 'strength` to fully operate the telechrenometeruna-idedlIf-the subscriber short circuits both o'- the windingsot'V the meter,ofv course it cannot beoperated, but the reduction of' the impedance otthe telephone circuit' caused by this short circuit increases thelcurrent suppliedto the circuit and thereby mak-es the detectionof theshortcircuit readily possible by the use of 'the usual and well knowntestinginstrument atthe command of the wire chiefj at the central olice.

In theidrawing I' have indicated by 'the V usual-circuitsymbolssufficient apparatus to enable a: clear-understanding of theinvention.

rlhesubscribers station A is equipped with the usual talkinginstrumentalities comprising-the transmitter X, the induction coil I,the receiver R and the-'hoor switch 4, together with the signal bellsv3v andthe telechronometer- T.` The mechanical construction of-'thetelechronometer can bestbe V405--understood from a reading of the abovementioned-copending application to which ret erence is here-made'forthose details. The electro-magnet of the telechronometer- T compriseswindings, 5 and 6, the winding 5 451 beingincl'uded in one side oi theline to the central oflice and the winding (5 in the opposite side.V

This telephone line term-inates'at the cenf tra-l oilice in the.V linerelay LRy and in the "ianswering'ljaclrs AJ and the calling jacksCJ,Ynot shown, as is the custom in a common battery telephone. system.

Responsive to the removalothe receiver R from the hook switch flA acircuitis completed from ground through the outer break springs on therelay COR, through the line conductor l and the winding 6 oi'- thetelechronometer T, through the transmitter X, the primary winding or"the induction -coilfl,through the winding 5 of the telechronometer,through the malte contacts of hook switch 4, threughthe line conductor2, through the inner break contacts of the cut-effi re-laiy, through thewinding of the #line relay to battery.A Theline relay energizes overthis circuit and closes the obvious circuit for the line lamp LL toindicate to the operator that the station A has initiated a call.

The operator picks up the answering plug Al) of the cord circuit CC andinserts it intothe answering jack AJ associated with the line A, therebycompleting` a` circuit from Grounded battery through the sleeve relay SRthrough the sleeve of the plug and jack AP and AJ through the winding oithe cut-oft2 relay COR to ground.

The cut-oh" relay energizes over this circuit and opens the circuit otsthe line relay LR to permit that relay to fall back and extinguish theline lampLL and teclear the line A ofl groundV andbatteryconnections. Asis well understood by those versed in the telephone art, the centralL@Hice-battery has one of" its poles permanently connected to the ground.

`Whenthe connection has' been so established, the transmittei'oii thesub-station A will be supplied with battery over a circuit extendinc'from the negative Jeleot'batter C1 b l through the resistors Rl and R3in parallel to the lower and upper terminals respectively ofthe relayAS, andl iroxn the positive terminal of battery wuich is also connectedto ground, through resistance unitsl R2 and ltfll in parallel to theopposite terminals respectively of' the answering supervisoryl relayVAS.

Since thel resistanceunit Ril'is a-t its maximum resistance value whenythe resistance unit; R2 is at its minimum value, the connection throughonset-'these resistors to one of the terminals of the relay AS will, ineffect, be nulliied. Assume for the moment that the resistance Reis thehigh reels' ance unit, the transmitter current then traverses thecircuit through resistance RQ'through the upper winding of thesupervising relay AS to the tip connection of the plug AP and the AJ,over the line conductor l throughy the upper winding (l oi'tlietelechronometer T`,`-through the transmitter X, through the primarywinding oli-the induction'coil I, through the lower winding 5 of thetelechrenometer, through hook switch spring 4l and its maize contact,through the line conductor 2 tothe ring connection et the jack AJ' andthe plug AP, through the lowerl vinding ofthe relay AS, through theresistance Rl, through the auinieter A, to thev negativeY gole ot'battery. t will be remembered that resistances Rl. and R2 are operatedas. a pair so that when R2 is low in Value will be corr spondingly lowin value.

The operatJr then throws the listening hey LK to connect her head setinto the circuit, ovcrwhich she can converse with 'the subscriber atstation A to ascertain what number he `is call-ing.

Cl? and jack CJ, through the line conductor' 2 of the line B, throughthe hook switch,

teleclirononieter winding, inductionV coil,

transmitter, and second telechronometer winding of the telephonesubstation B, kline conductor l leading therefrom, the tip conductor ofthe jack CJ and plug CP, the upper normally closed contacts of theringing key lili, through the upper winding of the calling supervisoryrelay CS, through the aiiimeter A to negative battery. It will be notedthat this connection does not include the resistance units lil-R4inclusive, and therefore that the battery supply current to thetransmitter of the sub-station B will not be reversed periodically.

rlhc cord circuit UO will contain other relays, lamps, keys, etc., as iscustomary with modern telephone cord circuits, but since theseinstruinentalities do not come within the scope of the presentinvention,

they have been omitted from the drawing to avoid an unnecessarycomplication thereof.

The parties A and B may now converse over the circuit just traced.

rllie plnngers 79 and 80 of the poleA changer associated with J@he cordcircuit CC are operated by the cylinders Z3 and 7 4 in the mannerpointed out in detail in the above mentioned copending application. Theplunger 79 is withdrawn from the resistance units R1 and while theplunger 8O is pressed against the units R3 and R4 and vice versa.

This reversal of current at the cord cir-V4 cuit CC operates thetelechronometer T through the windings 4 and 5 to register a Y chargeagainst the calling subscriber A indicative of the length of time thatthe telephone has been in use on the dials of the tel-echroncincter. Ifthe conversation continues, plungers 7 9 and 8O are re-operated in thereverse direction so that battery supply current is again reversed tothe transmitter X through the resistances VRl and R2, and thetelechronoinetei is again operated to assess another charge against thesubscriber in the manner pointed out in detail in the copendiiigapplication referred to above.

If the subscriber attempts to secure his telephone service withouthaving his telechronoineter T register the proper number of unitstherefor, he might endeavor to apply short-circuit to the winding 5 orto the winding 6 of his telechronometer. reptitious application of sucha. shortfcircuit, ifit'be to one of the windings, will not howeveraccomplish the purpose that the subscriber intended since each of thewindly to be capable of operating the telechronometer 'properly withoutthe assistance of the other Winding.

In the circuit previously traced for ther battery feed to thetransmitter X at station`=-f A, resistancesy R1 and R2 were assumedto beof low value,rand therefore relay AS had negative potential impressed onits lower winding and positive potential on its upper winding. In thiscase plunger 79 is pressing "85 against R1 and R2 and plunger 80 isretracted 'from R3 and R4.

After a predetermined time has elapsed, the positions of plungers 79 and8() arereversed by an operation of cylinders 73 and 74. Aslgo explainedin my above mentioned copending application, this reversal takes placerapidly. After this reversal resistances R1y and R2 have high value andR3 and R4 low value, the lower winding of AS has positivel'95 potentialimpressed upon it, and the uppery winding has negative potential uponit, which it will be noted is the reverse of the initial potentialstraced above.-

The wirechief could readilyascertain ifllo the winding wasshort-circuited by inserting a resistance meter in the circuit to thesubstation A, thereby measuring the loop resistance, it would be loweredby the short circuit ofthe winding. were'short-circuited there would bean appreciable reduction in the loop resistances and that fact wouldvbereadily ascertainable kby the corresponding 'increase in the transmittersupply currenthad over the line" circuit to the transmitter X.

4:[f the subscriber at'Station A attempts to disable the telechronometerTby grounding one or the other ide of the line, the presencem of thisground is readily detected sincenormally the two sides of the line arebalanced and free from ground. The application of ground to one orotlierside of the line would destroy the normal balance and could be readilypicked up by the usual volt meteff:

test devices well known and understood by those skilled in the art. y'

Having thus complied to the statutes and shown `and described apreferred embodi ment of my invention, what Iconsider new" 25 and desireto have protected by Letters Patent is pointed out in the appendedclaims.

VlVhat is claimed is:

l. lncombination, a telephone station having a pair of line wires,adapted. to leadtl The sur# 70 ings is Vsuiificiently strongelectro-magneticalg 75 If the two windings 5' 105 central,an*zele'cteofinagnetic devicef at :said

station; saidfeleetrmagnetic device inelud-v lingiza lpair =ozf= coilsconnected :serially leach-1n a limb( of the .telephone line and Laperma- 'sfinent'magnet l: adapted rto :be :actuated :by sind coils.

Y .agsenose i ,line thereby; rendering shortseircuiting of the'telechnenometer:readily. detectable.

'In -xwitnessiwhereof7 l hereunto subscribe .my naine this .25th.day-rotMarch, 1929.

GARRISONBABCQCIQ 2i In .combine-tien, a telephone station-hav-Jingaipair :of linenwires adapted to 4leadito im station, :said deviceincluding a"magnet,andv

a-pair of'lcoils. connected serial-ly each lin a :limb .fof the line and:acting -curnulativel-y to actuate the magnet in accordance Wiiththepolzxrity impressed upon the line..

1a `pair: Aof metal-lic conductors, anwelect'romagnetic device includingVa ,pai-r .of 'actu- 4ating4 coils each connectedvserially in oneconductor of ,said pair and .adapted for "12 energization together, andla permanent lnagnetrad'apted to rbe `aetnatedby 'said coils. 4. In atelephone system,- fthe combination of Ha' :subscribers :stationcomprising the 'us-ual :tallcinfg instrumentalities connected -;to

mndrni-lnetefr ha-Vingtwo eectricallyy independent, and :equalfrwindi-ngs, .one of which 1s l`ln1combination, ia telephone l,line:having:l

` "25 ,fa central '.oi'lice by a Ypair -of ,line conductors,

connectedl in :serial relation with each vof vsaid Yline condiicters.k

5: lin f a 'telephone rsysteln, the combination ofra snbsori'bersstation comprisingthe iusual talking instrumentalitiesconnected toacenytrai; oticefby pair of .line 2 conductors, @and a meter havingftwof-mechanicallyand elec- *(35 tricaflly. independent. windings 'of'identical electric -cliara-cteristics, oneof Ysaid -Wi-ndings :beingconnected in -ser1fi-l vrelation With cach-oil said conductors, :and amechanism 'operated responsive :to :ein -energization ofr Gu ln iatelephone system, the combina-tion :a :subscribes: station :comprisingthe usual nnstrnnientalitiesfconnecte'd ato a centrall office `eyfafpai'r vof line conductors, .two f windings of identical .electriccharacteristics,- fonezfo-fz said kwindings :being connected 1n i45'frnechaniealy and electrically independent;

'serial relation with each otssaid conductors7 iand a. mechanismoperated .responsive to an 'l 50-ene rgization of said windings byelectromagnetism set up; in saidl windings.

7.5 In na -telephone system, :the combination `o'ii'a' subscriber?sstationjcorrqrrising the usual instrumentallties connected ato a cen-55:-,tral office ove-.rxan umgrfounded y two conc'luotorY circuit; a.meterxhaving two electrically.. balanced windings, one connected 1neach fof-

